1. Field of the Invention
The present invention relates to an oscillating internally meshing planetary gear system.
2. Description of the Related Art
An oscillating internally meshing planetary gear system is widely used which has an internal gear and an external gear internally meshing with the internal gear. The gear system is configured such that one of the internal gear and the external gear is oscillatingly rotated by an eccentric body formed in an eccentric body shaft.
For example, a planetary gear system shown in FIG. 2 is disclosed in Japanese Patent Laid-Open Publication No. 2000-65162. This the planetary gear system 10 includes an input shaft 12, first and second eccentric bodies 14 and 16, first and second external gears 18 and 20, an internal gear 22, a relative rotation outputting mechanism K, and first and second supporting flanges 24 and 26 serving as an output element. In this instance, in order to achieve an increase in transmission capacity, the two first and second external gears 18 and 20 are arranged side by side in the axial direction.
The input shaft 12 is a hollow shaft having a large diameter hollow portion 12H and is disposed in a radially central portion of the planetary gear system 10. The input shaft 12 also serves as an eccentric body shaft, and each of the first and second eccentric bodies 14 and 16 is integrally formed with the outer periphery of the input shaft 12. The eccentric phases of the first and second eccentric bodies 14 and 16 are shifted relative to each other by 180 degrees.
The roller-shaped first and second sliding motion-facilitating members 34 and 36 intervene between the outer peripheries of the first and second eccentric bodies 14 and 16 and the first and second external gears 18 and 20, respectively. The input shaft (eccentric body shaft) 12 is supported by the first and second supporting flanges 24 and 26 through tapered roller bearings (eccentric body shaft bearings) 38 and 39.
The relative rotation outputting mechanism K is implemented by first and second inner pin holes 40 and 42 formed in the first and second external gears 18 and 20, respectively, an inner pin 44 passing through the inner pin holes 40 and 42, and an inner roller 43.
When the input shaft 12 is rotated by a motor (not shown), the first and second eccentric bodies 14 and 16 are eccentrically rotated integrally with the input shaft 12. Thus, while the input shaft 12 rotates one revolution, the external gears 18 and 20 mounted on the eccentric bodies 14 and 16, respectively, oscillate one cycle. Therefore, each of the first and second external gears 18 and 20 is rotated relative to the stationary internal gear 22 by an amount corresponding to the difference in the number of teeth from the internal gear 22. The relative rotation is outputted from the side of one of the first and second supporting flanges 24 and 26 as reduced speed output through the first and second inner pin holes 40 and 42, the inner roller 43, and the inner pin 44 (the relative rotation outputting mechanism K).
Also in the field of such planetary gear systems, there is a strong demand for improvement in basic performance and reduction in cost. Therefore, it is an object of the present invention to meet such a demand.